Near-field exposure mask, resist pattern forming method, device manufacturing method, near-field exposure method, pattern forming method, near-field optical lithography member, and near-field nanoimprint method

ABSTRACT

A near-field exposure mask according to an embodiment includes: a silicon substrate; and a near-field light generating unit that is formed on the silicon substrate, the near-field light generating unit being a layer containing at least one element selected from the group consisting of Au, Al, Ag, Cu, Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formed with layers made of some of those materials.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2011-51698 filed on Mar. 9, 2011in Japan, the entire contents of which are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a near-field exposuremask, a resist pattern forming method, a device manufacturing method, anear-field exposure method, a pattern forming method, a near-fieldoptical lithography member, and a near-field nanoimprint method.

BACKGROUND

In recent years, there have been increasing demands for devices withhigher densities and higher integration degrees in the fields of variouselectronic devices that require fine processing, such as semiconductordevices. To satisfy those demands, formation of finer patterns isessential. In procedures for manufacturing such semiconductor devices,the photolithography technology plays an important role in the formationof fine patterns.

To increase photolithography resolution, it is necessary to shorten thewavelength of the light source to be used for exposures or increase thenumerical aperture of the projector lens. When the numerical aperture isincreased, the resolution becomes higher, but the focal depth becomessmaller. As a result, predetermined resolution cannot be achieved withrespect to an exposure of a surface having concavities and convexitieswith a depth equal to or greater than the focal depth. Therefore, theflatness of the substrate needs to be increased. To form even finerpatterns, the wavelength λ of each light source is required to have ashorter wavelength. The wavelength λ of each light source used forexposures has been shortened from g-ray (436 nm) to i-ray (365 nm). Atpresent, excimer lasers (248 nm, 193 nm) are being mainly used as thelight sources. By the photolithography technology, however, thediffraction limit of a light source is the resolution limit. Therefore,even with the use of a 193-nm ArF excimer laser immersion exposuretechnique, it is difficult to form patterns of 10 nm or smaller inlinewidth.

To form even finer patterns, it is necessary to use the X-raylithography technology or the electron beam lithography technology. Bythe X-ray lithography technology, the resolution can be made ten or moretimes as high as the resolution achieved when an exposure is performedwith the use of an excimer laser. By the X-ray lithography technology,however, it is difficult to form a mask, and the device costs are high.

By the electron beam lithography technology, formation of patterns onthe order of nanometers can be controlled with high precision, and agreater focal depth than that of an optical system can be achieved. Theelectron beam lithography has the advantage that a pattern can be drawndirectly on a wafer without a mask. However, the electron beamlithography has low throughput, and is costly. Therefore, the electronbeam lithography is not suited to mass production.

Further, in lithography using an X-ray or an electron beam, it isnecessary to develop a resist in accordance with each exposure method,and there are a large number of problems in terms of sensitivity,resolution, etching endurance, and the like.

To solve those problems, there has been a suggested method in which bynear-field light leaking from openings with diameters sufficientlysmaller than the wavelength of the light to be emitted, a resist is thenexposed and developed, to form a fine pattern. This method ischaracterized by achieving a spatial resolving power on the order ofnanometers, regardless of the wavelength of the light source. The methodusing near-field light is not subjected to a restriction in terms of theoptical diffraction limit, and accordingly, is capable of achieving aspatial resolving power that is a third or less of the light sourcewavelength. Further, with the use of a mercury lamp or a semiconductorlaser as the light source, the size of the light source can be reduced.Accordingly, the device can be made smaller in size, and the costs canbe lowered.

As one of the lithography techniques using near-field light, there hasbeen a known method by which a near-field exposure mask having a lightshielding layer with openings smaller than the light source wavelengthis brought into contact with a resist so that the distance in betweenbecomes 100 nm or less, which is a near-field range, and the finepattern on the mask is transferred to the resist by a collectiveexposure. In this operation, the contact properties are critical. It isknown that a membrane mask can be used as the near-field exposure mask.It is also known that a resin mask can be used as the near-fieldexposure mask.

As a method of performing an exposure through contact with the use of amembrane mask, there has been a disclosed near-field exposure method bywhich the thickness of the mask is reduced to such a value that the maskcan be elastically deformed, and the mask is elastically deformed byapplying a controlled pressure onto the thinned portion so that theexposure mask is brought into contact with the substrate to be exposed.By this method, however, the required manufacturing process consists ofa large number of procedures for forming the mask having a thin-filmstructure, and the thinner portion of the mask might be broken at thetime of pressure application or pressure release.

By a method of performing an exposure with the use of a resin mask, onthe other hand, the contact between the mask and the light shieldinglayer is strong. Therefore, the mask might be broken at the time of maskdetachment, or the resist might come off the substrate.

When a resist such as a chemically-amplified resist or a photo cationpolymerizable resist that exhibits a development contrast through areaction with a catalyst that is the acid generated by an exposure, thelight shielding layer to be the mask is corroded by the generated acid.As a result, the life of the mask might be shortened.

As described above, conventional near-field masks have room forimprovement to achieve excellent contact properties with respect toto-be-exposed substrate over a large area, reduce the number ofprocedures in the manufacturing process, and increase the durability.

There has been a known method by which a near-field exposure isperformed by using resonant light with a light wavelength equivalent tothe resonant energy of the molecules forming a resist. The near-fieldexposure using resonant light is performed as follows.

A first substrate having a photoresist layer formed thereon, and a maskhaving a mask pattern formed on a transparent second substrate areprepared. The mask pattern is then brought into contact with the resistlayer. With the mask being in contact with the photoresist layer, ani-ray (365 nm) is emitted onto the back surface of the mask. As aresult, near-field light leaks from the openings of the mask pattern byvirtue of the i-ray irradiation, and an exposure is performed. Theexposed resist portions react to the light.

After the exposure, the mask is detached from the photoresist layer, andthe photoresist layer is developed with a developer. As a result, theexposed portions are dissolved, and a pattern is formed.

As another near-field exposure method, there has been a known method bywhich a near-field exposure is performed by using nonresonant light witha longer wavelength than the wavelength of light equivalent to theresonant energy of the molecules forming a resist. A mask patterntransfer through a near-field exposure using such a nonresonantwavelength is performed as follows. A resist layer is formed on a firstsubstrate, and a mask having a mask pattern with openings formed on atransparent second substrate is prepared. The mask pattern is thenbrought into contact with the resist layer. With the mask pattern beingin contact with the resist layer, nonresonant light having a longerwavelength than the wavelength of light equivalent to the resonantenergy of the molecules forming the resist is emitted on to the backsurface of the mask.

As a result, near-field light leaks from the openings of the maskpattern by virtue of the nonresonant light irradiation, but the resistlayer does not react to the nonresonant light. However, strongelectronic polarization occurs at the edge portions of the mask pattern,and near-field light is generated from the nonresonant light. Themolecules forming the resist get dissociated through excitation causedby multiple light absorptions by the near field light generated from thenonresonant light (a multistep transition process).

After the exposure, the mask is detached from the resist layer, and theresist layer is developed with a developer. As a result, the portionsexposed by the near-field light generated from the nonresonant light aredissolved, and a pattern is formed. The difference from an exposureusing resonant light is that a pattern is formed along the edge portionsof the mask pattern. Accordingly, a finer pattern can be formed with theuse of nonresonant light.

Since the photosensitive wavelength of the photoresist is in a visiblerange, a glass material is normally used as the transparent secondsubstrate. To increase the efficiency in the exposure process, the sizeof the transparent second substrate needs to be made larger. In recentyears, the sizes of wafers used in semiconductor manufacturing processesare 300 mm in diameter. Since the near-field exposure method usingnonresonant light is a contact exposure method, the size of thetransparent second substrate needs to be approximately 300 mm indiameter. Since the mask pattern and the resist layer need to be incontact with each other, the transparent second substrate should havelow surface roughness and small warpage.

However, where a glass material of approximately 300 mm in diameter isused as the transparent second substrate, it is difficult for the secondsubstrate to have sufficiently low surface roughness and small warpageover a large area. On the other hand, a Si wafer of 300 mm in diametercan have sufficiently low surface roughness and small warpage. However,such a Si wafer cannot be used as the mask, because visible light cannotpass through Si.

Further, at the time of an exposure, light from the light source entersperpendicularly to the first substrate. When the transparent secondsubstrate is made of glass, the reflectivity at the interface betweenthe air and the glass is 4%, and the loss of the incident light energyis small. However, the reflectivity at the interface between the air andSi is as high as 30%, and the exposure time becomes longer. Therefore,the productivity becomes lower in the exposure process.

Further, there has been a demand for higher-density microfabrication ofsemiconductor packages, interposers, printed circuit boards, and thelike, as semiconductors have been made to have smaller sizes, higherdensities, and higher speeds. Particularly, in recent years, at the timeof formation of a storage media fine structure pattern or formation of abiochip nanostructure, high-density microfabrication is more and morestrongly required. As a mass-production means to satisfy such atechnical demand, the nanoimprint technology has been studied in recentyears.

The nanoimprint technology has been developed by applying a pressingmethod using a metal mold to the nanoscale technology, and involves ananoscale mold processing technique for performing molding by pressing amold with minute concavities and convexities against an object to beprocessed. By the nanoimprint technology, patterns with a width ofseveral tens of nanometers can be formed. Compared with an equivalentprocessing technology using an electron beam, the nanoimprint technologyhas the advantage that a large number of patterns can be molded at verylow costs.

In the nanoimprint technology, the use of near-field light has beensuggested. Particularly, an ultrafine pattern of 10 nm or smaller can betransferred with high precision by the nanoimprint technology usingnear-field light. When a Si substrate is processed, light needs to beemitted onto a glass template. However, this irradiation directionlowers the near-field light generation efficiency.

The use of near-field light has also been suggested for template andpattern forming methods based on the nanoimprint technology. However,when a fine pattern is transferred, the contact between the template andthe Si substrate needs to be improved. Therefore, there is still roomfor improvement to develop an optimum pattern forming method.

The present invention has been made in view of these circumstances, andan object thereof is to provide a near-field exposure mask that cansecure contact between a mask and a to-be-exposed object over a largearea, a resist pattern forming method, and a device manufacturingmethod.

Another object of the present invention is to provide a near-fieldexposure method by which the exposure time can be shortened.

Yet another object of the present invention is to provide a patternforming method by which an ultrafine pattern can be transferred onto aSi substrate with high precision.

Still another object of the present invention is to provide ahigh-precision near-field optical lithography technique that can realizedouble patterning with high efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) through 1(f) are cross-sectional views illustratingprocedures for manufacturing a near-field exposure mask according to afirst embodiment;

FIGS. 2( a) and 2(b) are cross-sectional views showing a near-fieldexposure apparatus according to a second embodiment;

FIGS. 3( a) through 3(d) are cross-sectional views illustrating a resistpattern forming method and a device manufacturing method according to athird embodiment;

FIGS. 4( a) through 4(e) are cross-sectional views for explaining anear-field exposure method according to a fourth embodiment;

FIGS. 5( a) through 5(c) are cross-sectional views for explaining anear-field exposure method according to the fourth embodiment;

FIG. 6 is a diagram showing the dependence of the resistivity on theincident angle;

FIGS. 7( a) and 7(b) are cross-sectional views for explaining anear-field exposure method according to the fourth embodiment;

FIGS. 8( a) through 8(d) are cross-sectional views for explaining anear-field exposure method according to a fifth embodiment;

FIG. 9 is a graph showing the ratio of the incident light propagating ina Si substrate with respect to the incident angle;

FIGS. 10( a) through 10(e) are cross-sectional views for explaining anear-field exposure method according to a sixth embodiment;

FIGS. 11( a) through 11(d) are cross-sectional views for explaining anear-field exposure method according to the sixth embodiment;

FIGS. 12( a) through 12(e) are cross-sectional views for explaining anear-field exposure method according to a seventh embodiment;

FIGS. 13( a) through 13(e) are cross-sectional views for explaining anear-field exposure method according to an eighth embodiment;

FIGS. 14( a) through 14(e) are cross-sectional views for explaining anear-field exposure method according to a ninth embodiment;

FIGS. 15( a) through 15(e) are cross-sectional views for explaining anear-field exposure method according to a tenth embodiment;

FIGS. 16( a) through 16(e) are cross-sectional views for explaining apattern forming method according to an eleventh embodiment;

FIGS. 17( a) through 17(c) are cross-sectional views for explaining apattern forming method according to the eleventh embodiment;

FIG. 18 is a photograph showing the near-field light generated at theedge portions in a pattern by the method according to the eleventhembodiment;

FIG. 19 is a table showing examples of the eleventh embodiment;

FIG. 20 is a table showing comparative examples of the eleventhembodiment;

FIG. 21 is a cross-sectional view for explaining a near-field opticallithography method according to a twelfth embodiment;

FIGS. 22A through 22D are graphs showing the distributions of lightintensities of samples 1 through 4; and

FIGS. 23( a) and 23(b) are diagrams for explaining formation of anear-field light generating layer.

DETAILED DESCRIPTION

A near-field exposure mask according to an embodiment includes: asilicon substrate; and a near-field light generating unit formed on thesilicon substrate, the near-field light generating unit being a layercontaining at least one element selected from the group consisting ofAu, Al, Ag, Cu, Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a filmstack formed with layers made of some of those materials.

The following is a description of embodiments, with references to theaccompanying drawings.

First Embodiment

Referring to FIGS. 1( a) through 1(f), a near-field exposure maskaccording to a first embodiment is described. FIGS. 1( a) through 1(f)are cross-sectional views illustrating the procedures for manufacturingthe near-field exposure mask according to the first embodiment.

First, a silicon substrate 2 of 600 μm in thickness is prepared, and aresist layer 4 of 10 nm to 30 nm in thickness, for example, is appliedonto the silicon substrate 2 (FIGS. 1( a) and 1(b)). A resist pattern 4a is then formed in the resist layer 4 by using an electron beamlithography technique or an Extreme Ultra-Violet (EUV) lithographytechnique (FIG. 1( c)). This resist pattern 4 a is a line-and-spacepattern in which the line width W₁ is nm, and the space width W₂ is 10nm, for example. Accordingly, the height of the resist pattern 4 a is 10nm to 30 nm.

After that, a near-field light generating film 6 is deposited on theresist pattern 4 a, to fill the spaces in the resist pattern 4 a (FIG.1( d)). The near-field light generating film 6 may be a layer containingat least one element selected from the group consisting of Au, Al, Ag,Cu, Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formedwith layers made of some of those materials.

By using Chemical Mechanical Polishing (CMP), the near-field lightgenerating film 6 is polished, and the upper surface of the resistpattern 4 a is exposed (FIG. 1( e)). After that, the resist pattern 4 ais removed by using a resist remover, to form a near-field exposure mask1 (FIG. 1( f)).

The near-field exposure mask 1 formed in this manner includes anear-field light generating film pattern 6 a formed on the siliconsubstrate 2. The near-field light generating film pattern 6 a is aline-and-space pattern in which the line width W₂ is 10 nm, and thespace width W₁ is 10 nm, for example. Accordingly, the height (thethickness) of the lines in the near-field light generating film pattern6 a is 10 nm to 30 nm. The height (the thickness) of the lines in thenear-field light generating film pattern 6 a is 100 nm or smaller sothat near-field light reaches the resist to be exposed, but ispreferably 50 nm or smaller. Alternatively, the near-field lightgenerating film pattern 6 a may be a pattern in which the line width W₂is 5 nm or greater, and the space width W₁ is 5 nm or greater. It shouldbe noted that the preferred sizes in the near-field light generatingfilm pattern 6 a vary with devices to be formed by using the near-fieldexposure mask.

To secure contact between the mask 1 and the object to be exposed over alarge area, the thickness of the silicon substrate 2 used as the matrixfor the near-field exposure mask 1 is preferably 300 μm to 1 mm.

In this embodiment, the mask 1 is formed with the silicon substrate 2and the near-field light generating film pattern 6 a. Accordingly, thedurability can be increased, and the mask 1 can be formed through simplemanufacturing procedures.

Second Embodiment

Referring now to FIGS. 2( a) and 2(b), a near-field exposure apparatusaccording to a second embodiment is described. The near-field exposureapparatus 20 of the second embodiment performs exposures, using thenear-field exposure mask 1 of the first embodiment. The near-fieldexposure apparatus 20 includes: a mount table 22 a on which ato-be-exposed substrate (a to-be-processed substrate) 12 having a resist14 applied thereto is placed, a supporting table 22 b that supports theface of the near-field exposure mask 1 on which the near-field lightgenerating film pattern 6 a is formed; and a mask 24 to allow light froma light source 26 to irradiate the region of the near-field exposuremask 1 on which the near-field light generating film pattern 6 a isformed. As shown in FIGS. 2( a) and 2(b), light is emitted from thelight source 26 located on the silicon substrate side of the near-fieldexposure mask 1, and the near-field light generating film pattern 6 aand the resist 14 applied onto the to-be-exposed substrate 12 arepositioned to face each other.

FIG. 2( a) is a cross-sectional view showing a situation where thenear-field light generating film pattern 6 a of the near-field exposuremask 1 is not in contact with the resist 14 applied onto theto-be-exposed substrate 12. FIG. 2( b) is a cross-sectional view showinga situation where the near-field light generating film pattern 6 a ofthe near-field exposure mask 1 is in contact with the resist 14 appliedonto the to-be-exposed substrate 12.

The near-field exposure apparatus 20 of the second embodiment includesthe light source 26 used for near-field exposures, and a contactingmechanism 28 (such as a vacuum pump) for bringing the near-field lightgenerating film pattern 6 a of the near-field exposure mask 1 intocontact with the resist 14 applied onto the to-be-exposed substrate 12.

When the near-field light generating film pattern 6 a is not in contactwith the resist 14 applied onto the to-be-exposed substrate 12 as shownin FIG. 2( a), the contacting mechanism 28 does not operate, and thelight source 26 is in an OFF state. On the other hand, when thenear-field light generating film pattern 6 a is in contact with theresist 14 applied onto the to-be-exposed substrate 12 as shown in FIG.2( b), the contacting mechanism 28 operates, and the light source 26 isin an ON state. That is, by activating the contact mechanism 28, thenear-field light generating film pattern 6 a is brought into contactwith the resist 14. With the near-field light generating film pattern 6a being in contact with the resist 14, the back surface of thenear-field exposure mask 1 is irradiated with the light from the lightsource 26. It should be noted that the light source 26 needs to be alight source that generates light of 1100 nm or longer in wavelength,because light of 1100 nm or longer in wavelength can pass through Si.

As a result, near-field light is generated from the opening portions ofthe near-field light generating film pattern 6 a of the near-fieldexposure mask 1, and a pattern latent image is transferred to the resist14 on the to-be-exposed substrate 12. The exposure is preferablyperformed where the near-field exposure mask 1 and the resist 14 formedon the to-be-exposed substrate 12 are in close contact with each other(without any non-contact region) in the area in which the pattern is tobe formed. In the second embodiment, exposures are performed with lightentering from the opposite side from the side on which the near-fieldlight generating film pattern 6 a of the near-field exposure mask 1 isformed. However, as will be described later, exposures may be performedwith light entering from the side on which the near-field lightgenerating film pattern 6 a of the near-field exposure mask 1 is formed.

As the resist 14 used in the second embodiment, either a positive resistor a negative resist can be used. Examples of positive resists that canbe used include a diazonaphthoquinone-novolac resist and achemically-amplified positive resist. Examples of negative resists thatcan be used include a chemically-amplified negative resist, a photocation polymerizable resist, a photo radical polymerizable resist, apolyhydroxystyrene-bisazide resist, a cyclized rubber-bisazide resist,and a polyvinyl cinnamate resist. With the use of a chemically-amplifiedpositive resist and a chemically-amplified negative resist, a patternwith a low line edge roughness is formed. Accordingly, the use of achemically-amplified positive resist or a chemically-amplified negativeresist is particularly preferable in this embodiment.

In this embodiment, a known light source can be used as the near-fieldlight source 26. For example, a laser having a wavelength of 1 μm to 20μm can be used. One or more such light sources can be used. Sincesemiconductor lasers are less expensive, high-power lasers, the use of asemiconductor laser is more preferable in this embodiment.

Third Embodiment

Referring now to FIGS. 3( a) through 3(d), a resist pattern formingmethod and a device manufacturing method according to a third embodimentare described.

In the third embodiment, the near-field exposure mask 1 of the firstembodiment and the near-field exposure apparatus 20 of the secondembodiment are used, for example.

First, the to-be-processed substrate 12 is prepared, and the resistlayer 14 is applied onto the to-be-processed substrate 12. The resistlayer 14 may be a single layer. In this embodiment, however, the resistlayer 14 is a double-layer resist structure formed by stacking a firstresist layer 15 and a second resist layer 16 in this order on theto-be-processed substrate 12. After that, the to-be-processed substrate12 and the near-field exposure mask 1 according to the first embodimentare placed and arranged on the near-field exposure apparatus (not shown)according to the second embodiment in such a manner that the near-fieldlight generating film pattern 6 a of the near-field exposure mask 1faces the resist layer 14 on the to-be-processed substrate 12 (FIG. 3(a)). The near-field light generating film pattern 6 a of the near-fieldexposure mask 1 and the resist layer 14 on the to-be-processed substrate12 are brought into contact with each other, and a near-field exposureis performed. As a result, near-field light leaks along the edgeportions of the near-field light generating film pattern 6 a, to exposethe resist layer 14. In this embodiment, the resist layer 14 is adouble-layer structure. Therefore, the upper resist layer 16 is exposedwith the near-field light.

The near-field exposure mask 1 is then detached from the to-be-processedsubstrate 12, and the exposed resist layer 16 is developed. As a result,a resist pattern 16 a is formed on the resist layer 15, as shown in FIG.3( b). With the resist pattern 16 a being used as a mask, patterning isperformed on the resist layer 15 by using a lithography technique, toform a resist pattern 15 a (FIG. 3( c)). As a result, a resist pattern14 a having a stack structure formed with the resist pattern 15 a andthe resist pattern 16 a is formed on the to-be-processed substrate 12(FIG. 3( c)).

With the resist pattern 14 a being used as a mask, dry etching or wetetching are performed. After the mask is removed, a semiconductorprocess including metal vapor deposition, lift-off, and plating isperformed on the to-be-processed substrate 12, to process theto-be-processed substrate 12. In this manner, a desired device is formedin the to-be-processed substrate 12.

As the resist layer 14 used in this embodiment, either a positive resistor a negative resist can be used, as long as it has photosensitivity tothe light source to be used. Examples of positive resists that can beused include a diazonaphthoquinone-novolac resist and achemically-amplified positive resist. Examples of negative resists thatcan be used include a chemically-amplified negative resist, a photocation polymerizable resist, a photo radical polymerizable resist, apolyhydroxystyrene-bisazide resist, a cyclized rubber-bisazide resist,and a polyvinyl cinnamate resist. With the use of a chemically-amplifiedpositive resistor and a chemically-amplified negative resist, a patternwith high linewidth accuracy is formed.

As the to-be-processed substrate 12, various kinds of substrates can beused, such as a semiconductor substrate made of Si, GaAs, InP, or thelike, an insulating substrate made of glass, quartz, BN, or the like, orany of those substrates on which one or more films made of a resist, ametal, an oxide, or a nitride are formed.

The propagation depth of near-field light is normally 100 nm or less. Toform the resist pattern 14 a of 100 nm or more in height by near-fieldoptical lithography, a resist layer having a multilayer structure ispreferably used. That is, it is preferable to use the resist layer 14having a double-layer structure in which the resist layer 16 havingendurance to oxygen dry etching is applied onto the lower resist layer15 that is applied onto the to-be-processed substrate 12 and can beremoved by dry etching. Alternatively, it is possible to use a resistlayer having a three-layer structure in which an oxygen plasma etchingendurance layer (not shown) is formed on the lower resist layer 15 thatis applied onto the to-be-processed substrate 12 and can be removed bydry etching, and the resist layer 16 is further applied onto the oxygenplasma etching endurance layer.

The applications of the resists 14, 15, and 16 can be performed by usingknown application apparatuses such as a spin coater, a dip coater, and aroller coater, and known methods.

The film thicknesses are comprehensively determined by taking intoaccount the processing depth of the to-be-processed substrate 12, andthe plasma etching endurances and light intensity profiles of theresists. Normally, the applications are preferably performed so that thefilm thicknesses fall within the range of 10 nm to 300 nm after prebake.

Further, prior to the applications of the resists 14, 15, and 16, one ormore of the following high-boiling-point solvents may be added to reducethe film thicknesses after the prebake: benzyl ethyl ether, di-n-hexylether, diethylene glycol monomethyl ether, diethylene glycol monoethylether, acetonylacetone, isophorone, capronic acid, caprylic acid,1-octanol, 1-nonanol, benzyl alcohol, benzyl acetate, ethyl benzoate,diethyl oxalate, diethyl maleic acid, γ-butyrolactone, ethylenecarbonate, propylene carbonate, ethylene glycol monophenyl etheracetate, and the like.

After the application, the resist layers are prebaked at 80° C. to 200°C., or more preferably, at 80° C. to 150° C. In the prebake, a heatingmeans such as a hot plate or a hot air drying machine can be used.

After the near-field exposure, post-exposure heating is performed. Thepost-exposure heating is performed at 80° C. to 200° C., or morepreferably, at 80° C. to 150° C. In the post-exposure heating, a heatingmeans such as a hot plate or a hot air drying machine can be used.

After the to-be-processed substrate 12 is heated as needed, the resistlayers subjected to the near-field exposure is developed with analkaline aqueous solution, an aqueous developer, an organic solvent, orthe like. Examples of development methods that can be used include a dipmethod, a spray method, a brushing method, and a slapping method. Inthis manner, a near-field resist pattern is formed.

When the resist pattern 16 a formed through a near-field exposure ismade to have a high aspect ratio by a resist layer having a double-layerstack structure, oxygen plasma etching is performed, with the pattern 16a being used as a mask. Examples of oxygen-containing gases that can beused in the oxygen plasma etching include oxygen, a mixed gas of oxygenand an inert gas such as an argon gas, or a mixed gas of oxygen andcarbon monoxide, carbon dioxide, ammonia, dinitrogen monoxide, sulfurdioxide, or the like.

When the resist pattern 16 a formed through a near-field exposure ismade to have a high aspect ratio by a resist layer having a three-layerstack structure, etching is performed on the oxygen plasma etchingendurance layer, with the pattern 16 a being used as a mask. Wet etchingor dry etching may be performed as the etching. However, dry etching ismore suitable for forming fine patterns, and therefore, is morepreferable.

As the wet etching agent, a hydrofluoric acid solution, an ammoniumfluoride aqueous solution, a phosphoric acid aqueous solution, an aceticacid aqueous solution, a nitric acid aqueous solution, a cerium ammoniumnitrate aqueous solution, or the like can be used, depending on theobject to be etched.

Examples of gases for the dry etching include CHF₃, CF₄, C₂F₆, CF₆,CCl₄, BCl₃, Cl₂, HCl, H₂, and Ar, and a combination of some of thosegases can be used as needed.

After the etching of the oxygen plasma etching endurance layer, oxygenplasma etching is performed in the same manner as in the case of aresist layer having a double-layer stack structure, and the pattern istransferred to the lower resist layer 15.

By using the device manufacturing method according to this embodiment,the following devices or elements (1) through (6) can be manufactured:

(1) a semiconductor device;

(2) a quantum dot laser element having a structure in which GaAs quantumdots of 50 nm in size are two-dimensionally arranged at 50-nm intervals;

(3) a subwavelength structure (SWS) in which conical SiO₂ members of 50nm in size are two-dimensionally arranged at 50-nm intervals on a SiO₂substrate, and a light reflection preventing function is provided;

(4) a photonic crystal optical device or a plasmon optical device havinga structure in which 100-nm members made of GaN or a metal aretwo-dimensionally and periodically arranged at 100-nm intervals;

(5) a biosensor element or a micro total analysis system (μTAS) elementthat has a structure in which Au fine particles of 50 nm in size aretwo-dimensionally arranged at 50-nm intervals on a plastic substrate,and uses local plasmon resonance (LPR) or surface-enhanced Ramanspectroscopy (SERS); and

(6) a nanoelectromechanical system (NEMS) element such as a SPM probehaving a sharp structure that is used in scanning probe microscopes(SPM) such as a tunnel microscope, an atomic force microscope, and anear-field optical microscope, and are of 50 nm or less in size.

Example

The following is a description of an example of the third embodiment.

A to-be-processed substrate having a resist applied thereto was placedon the side of the near-field light generating film pattern of anear-field exposure mask. The to-be-processed substrate 12 used here isa silicon substrate. As the resist, an i-ray resist was used. The resistwas applied onto the silicon substrate by a spin coater, and was bakedon a hot plate at an atmospheric temperature of 90° C. for 90 seconds,which was the heat treatment period. The film thickness of the resistlayer was 100 nm. An exposure was performed, while the near-fieldexposure mask and the to-be-exposed substrate were in close contact witheach other (without any non-contact region) in the area in which thepattern was to be formed.

A 1.5-μm infrared laser was used as the light source for the near-fieldexposure. The illumination intensity was approximately 85 mJ/cm² in thei-ray on the upper surface of the mask.

The to-be-processed substrate subjected to the near-field exposure wasimmersed in a 2.38% tetramethylammonium hydroxide aqueous solution for10 seconds at room temperature, and was thus developed. A line-and-spacepattern of 20 nm in half pitch and approximately 100 nm in depth wasobtained where the exposure time was two minutes, and a line-and-spacepattern of 50 nm in half pitch and approximately 100 nm in depth wasobtained when the exposure time was one minute.

Fourth Embodiment

Referring now to FIGS. 4( a) through 7(b), a near-field exposure methodaccording to a fourth embodiment is described. The near-field exposuremethod according to the fourth embodiment is a method for shortening theexposure time by lowering the reflectivity at the interface between theair and Si.

First, as shown in FIG. 4( a), a resist layer 54 is formed on a siliconsubstrate (also referred to as a Si substrate) 52 by using a spincoating technique. Although a spin coating technique is used as theresist forming method in this embodiment, the resist forming method isnot limited to that technique. As the resist, an i-ray resist is used,and the thickness of the resist layer 54 is approximately 50 nm.Although the thickness of the i-ray resist layer 54 is 50 nm in thisembodiment, it is not limited to 50 nm.

As shown in FIG. 4( a), a near-field exposure mask 61 having anear-field light generating film pattern 66 a formed on the Si substrate62 is prepared, and is positioned so that the resist layer 54 and thenear-field light generating film pattern 66 a face each other. Thenear-field exposure mask 61 is manufactured in the following manner. Asshown in FIG. 4( b), a resist 64 is applied onto the Si substrate 62. Apattern 64 b irradiated by electron beam irradiation is then drawn onthe resist 64 by an electron beam lithography apparatus (FIG. 4( c)). Atthis point, in the resist 64, there exist regions 64 a not irradiated byelectron beam irradiation. The pattern formation is not necessarilyperformed by an electron beam lithography apparatus. After the pattern64 b is drawn, a development is performed with a developer. After thedevelopment, cleaning is performed with ultrapure water, and moisture isremoved by an air blow. As a result, a pattern 64 a formed with theregions not irradiated by electron beam irradiation is left. As theresist 64, it is possible use a material from which a pattern formedwith regions not irradiated by electron beam irradiation is removed, anda pattern formed with regions irradiated by electron beam irradiation isnot removed. A near-field light generating film 66 is formed on the Sisubstrate having the pattern 64 a formed thereon by a vapor depositiontechnique or a sputtering technique. Cr is used as the material of thenear-field light generating film 66, and a mask with a line width of 200nm, a space width of 200 nm, and a height of 40 nm is formed. Theremaining resist 64 a is removed by an organic solvent such as acetone.FIG. 4( e) shows the completed near-field exposure mask 61.

As shown in FIG. 5( a), the near-field light generating film pattern 66a of the near-field exposure mask 61 is brought into contact with theresist layer 54. As shown in FIG. 5( b), light of 1550 nm in wavelengthis emitted onto the back surface of the mask 61. At this point, if thelight is emitted obliquely, the reflectivity at the interface betweenthe air and the Si substrate 62 of the mask 61 can be lowered. Theincident polarized light for generating near-field light at the edgeportions of the near-field light generating film pattern 66 a isp-polarized light. The reflectivity R_(p) at the interface between theair and the Si substrate 62 is expressed by the following mathematicalformulas (1):

$\begin{matrix}{{R_{p} = {\frac{{N_{ti}^{2}\cos \; \theta_{i}} - \sqrt{N_{ti}^{2} - {\sin^{2}\theta_{i}}}}{{N_{ti}^{2}\cos \; \theta_{i}} + \sqrt{N_{ti}^{2} - {\sin^{2}\theta_{i}}}}}^{2}},{N_{ti} = {\frac{N_{t}}{N_{i}} = \frac{n_{t} + {\kappa}_{i}}{n_{i} + {\kappa}_{i}}}}} & (1)\end{matrix}$

Here, N_(t) represents the complex refractive index of Si, and N_(i)represents the complex refractive index of the air. N_(ti) representsthe ratio between the complex refractive indexes. Further, n_(t)represents the refractive index of Si, κ_(t) represents the extinctioncoefficient of Si, n_(i) represents the refractive index of the air,κ_(i) represents the extinction coefficient of the air, and θ_(i)represents the incident angle. Where n_(t) is set to 3.48, κ_(t) is 0,n_(i) is 1, and κ_(i) is 0, so as to determine the reflectivity at theinterface between the air and the Si substrate, the dependence of thereflectivity R_(p) on the incident angle θ_(i), shown in FIG. 6, isobtained.

As can be seen from FIG. 6, the reflectivity is lowered to approximately10⁻⁶ particularly where the incident angle is 74 degrees, which is muchlower than the reflectivity in the case of vertical incidence. Further,where the incident angle is not 74 degrees, the reflectivity becomeshigher, and the exposure time becomes longer accordingly. To perform theexposure process with high efficiency, the incident angle is preferably57 to 82 degrees, so that the reflectivity becomes 10% or lower.

As a result, as shown in FIG. 7( a), a large amount of incident lightpropagates in the Si substrate 62, and near-field light is efficientlygenerated at the edge portions of the near-field light generating filmpattern 66 a of the near-field exposure mask 61. The resist portions 54a in the vicinities of the portions 68 at which the near-field light isgenerated become dissociated through a multistep transition process. Inthe fourth embodiment, a LED of 1550 nm in wavelength is used, and a1-hour exposure is performed with an incident power of 60 mW. The Sisubstrate 52 having the exposed resist layer 54 is immersed in adeveloper, and a 30-second development is performed. Cleaning is thenperformed with pure water, and moisture is removed by an air blow. Asshown in FIG. 7( b), the exposed resist portions 54 a are dissolved inthe developer, to form groove portions 55. Accordingly, a pattern 54 bhaving a width of 50 nm and a depth of 50 nm, which correspond to theedge portions of the near-field light generating film pattern 66 a ofthe near-field exposure mask 61, can be formed on the Si substrate 52.The depth of 50 nm corresponds to the leakage length of the intensity ofthe near-field light generated at the edge portions of the near-fieldlight generating film pattern 66 a of the near-field exposure mask 61.

As described above, according to the fourth embodiment, the reflectivityat the interface between the air and Si can be lowered, and the exposuretime can be shortened.

Fifth Embodiment

In the fourth embodiment, exposures are performed by irradiating theback surface of the near-field exposure mask 61 (the surface of the Sisubstrate on the opposite side from the side on which the near-fieldlight generating film pattern 66 a is formed) with light. On the otherhand, a near-field exposure method according to a fifth embodiment is amethod of irradiating the surface of the near-field exposure mask 61, orthe surface on which the near-field light generating film pattern 66 ais formed, with light. Referring now to FIGS. 8( a) through 8(d), thenear-field exposure method according to the fifth embodiment isdescribed.

First, as shown in FIG. 8( a), a resist layer 54 is formed on a Sisubstrate 52 by using an application technique such as a spin coatingtechnique, as in the fourth embodiment. As shown in FIG. 8( a), anear-field exposure mask 61 having a near-field light generating filmpattern 66 a formed on the Si substrate 62 is prepared. The near-fieldexposure mask 61 has the same structure as that used in the fourthembodiment.

As shown in FIG. 8( b), the near-field light generating film pattern 66a is then brought into contact with the resist layer 54. As shown inFIG. 8( c), light of 1550 nm in wavelength is then emitted onto thefront surface of the near-field exposure mask 61. The incident polarizedlight is p-polarized light. The incident light enters at an obliqueangle θ_(i). The light propagates in the resist layer 54, but thewavelength used here is much longer than the wavelength with whichresists are exposed. Therefore, no exposures are performed. However, thelight that reaches the interface between the near-field light generatingfilm pattern 66 a of the near-field exposure mask 61 and the resistlayer 54 is converted into near-field light 69 at the edge portions ofthe near-field light generating film pattern 66 a. The resist portions54 a in the vicinities of the regions in which the near-field light 69is generated are dissociated through a multistep transition process.Accordingly, a fine pattern can also be formed when light is emittedonto the front surface of the near-field exposure mask 61.

To generate near-field light efficiently at the edge portions of thenear-field light generating film pattern 66 a of the near-field exposuremask 61 when light of 1550 nm in wavelength is emitted onto the backsurface of the near-field exposure mask 61, the reflectivity at theinterface between the air and the Si substrate 62 needs to be lowered,and the amount of light propagating to the edge portions of thenear-field light generating film pattern 66 a needs to be increased. Inthe fifth embodiment, by using the formulas (1) as in the fourthembodiment, the ratio of the incident light propagating in the Sisubstrate 52 to the incident angle θ can also be calculated, as shown inFIG. 9. Here, the refractive index of the resist layer 54 is 1.70, andthe extinction coefficient is 0. As can be seen from FIG. 9, where theincident angle is 38 degrees, a transmissivity of 77% is obtained, andthe light amount becomes 45% larger than that in the case of verticalincidence. Further, where the incident angle is not 38 degrees, thetransmissivity becomes lower, and the exposure time becomes longeraccordingly. To efficiently perform the exposure process, the incidentangle is preferably 26 to 47 degrees, so that the transmissivity becomes90% or higher. As a result, as shown in FIG. 8( d), a large amount ofincident light propagates in the resist layer 54, and the near-fieldlight 69 is efficiently generated at the edge portions of the near-fieldlight generating film pattern 66 a. The resist portions 54 a in thevicinities of the regions in which the near-field light 69 is generatedare dissociated through a multistep transition process. A LED of 1550 nmin wavelength is used as the injection light source, and a 2-hourexposure is performed with an incident power of 30 mW. The Si substrate52 having the exposed resist layer 54 is immersed in a developer, and a30-second development is performed. Cleaning is then performed with purewater, and moisture is removed by an air blow. The exposed resistportions 54 a are dissolved in the developer, and a patterncorresponding to the edge portions of the near-field light generatingfilm pattern 66 a is formed. Accordingly, a pattern having a width of 50nm and a depth of 50 nm, which correspond to the edge portions of thenear-field light generating film pattern 66 a can be formed.

When light is emitted onto the front surface of the near-field exposuremask 61 as in the fifth embodiment, near-field light is more readilygenerated at the edge portions of the near-field light generating filmpattern 66 a of the near-field exposure mask 61 than when light isemitted onto the back surface of the near-field exposure mask 61 as inthe fourth embodiment. This is because, when light is emitted onto theback surface of the near-field exposure mask 61, near-field light isgenerated at the edge portions of the near-field light generating filmpattern 66 a on the side of the Si substrate 62, and the near-fieldlight moves to the edge portions of the near-field light generating filmpattern 66 a on the side of the resist layer 54, to expose the resistlayer 54. While the near-field light is moving from the edge portions ofthe near-field light generating film pattern 66 a on the side of the Sisubstrate 62 to the edge portions of the near-field light generatingfilm pattern 66 a on the side of the resist layer 54, part of thenear-field light is absorbed by the near-field light generating filmpattern 66 a, and the intensity of the near-field light becomes lower.In the case where light is emitted onto the front surface of thenear-field exposure mask 61, near-field light is generated at the edgeportions of the near-field light generating film pattern 66 a on theside of the resist layer 54 after propagating in the resist layer 54.Accordingly, the decrease in the intensity of the near-field light bythe near-field light generating film pattern 66 a is not caused as inthe case where light is emitted onto the back surface of the near-fieldexposure mask 61.

As described above, according to the fifth embodiment, the reflectivityat the interface between the air and Si can be lowered, and the exposuretime can be shortened.

Sixth Embodiment

In the first and second embodiments, Cr is used as the material of thenear-field light generating film pattern 66 a. However, a near-fieldexposure method according to a sixth embodiment is a method by which Auis used as the material of the near-field light generating film pattern66 a. Referring now to FIGS. 10( a) through 11(d), the near-fieldexposure method according to the sixth embodiment is described.

First, as shown in FIG. 10( a), a resist layer 54 is formed on a Sisubstrate 52 by an application technique such as a spin coatingtechnique, as in the fourth embodiment. As shown in FIG. 10( a), anear-field exposure mask 61A that is made of Au and has a near-fieldlight generating film pattern 67 a formed on a Si substrate 62 isprepared.

The near-field exposure mask 61A is manufactured in the followingmanner. As shown in FIG. 10( b), a resist layer 64 is applied onto theSi substrate 62. As shown in FIG. 10( c), a pattern 64 b is then drawnon the resist layer 64 by an electron beam lithography apparatus (notshown), for example. The pattern formation is not necessarily performedby an electron beam lithography apparatus. After the pattern 64 b isdrawn, the resist layer 64 is developed with the use of a developer.After the development, cleaning is performed with ultrapure water, andmoisture is removed by an air blow. As a result, a pattern 64 a formedwith the regions not irradiated by electron beam irradiation is left onthe Si substrate 62. After that, as shown in FIG. 10( d), a near-fieldlight generating film 67 is formed on the Si substrate 62 having thepattern 64 a formed thereon by a vapor deposition technique or asputtering technique. Au is used as the material of the near-field lightgenerating film 67, and a pattern 67 a with a line width of 100 nm, aspace width of 100 nm, and a height of 40 nm is formed. The remainingresist 64 a is removed by an organic solvent such as acetone. FIG. 10(e) shows the completed near-field exposure mask 61A.

The near-field light generating film pattern 67 a of the near-fieldexposure mask 61A formed in the above manner is brought into contactwith the resist layer 54 (FIG. 11( a)). As shown in FIG. 11( b), a LEDof 1550 nm in wavelength is used, and the upper face (the back surface)of the near-field exposure mask 61A is exposed for fifteen minutes withan incident power of 60 mW. The incident polarized light is p-polarizedlight, and the incident angle is 74 degrees.

Near-field light 68 is generated at the edge portions of the near-fieldlight generating film pattern 67 a of the near-field exposure mask 61A.The resist portions 54 a in the vicinities of the portions at which thenear-field light 68 is generated become dissociated through a multisteptransition process. The exposed sample is developed for 30 seconds witha developer. Cleaning is then performed with pure water, and moisture isremoved by an air blow. As shown in FIG. 11( d), the exposed resistportions 54 a are dissolved in the developer, to form a pattern 54 bhaving a width of 50 nm and a depth of 50 nm, which correspond to theedge portions of the near-field light generating film pattern 67 a.

As described above, according to the sixth embodiment, the reflectivityat the interface between the air and Si can be lowered, and the exposuretime can be shortened.

Seventh Embodiment

Referring now to FIGS. 12( a) through 12(e), a near-field exposuremethod according to a seventh embodiment is described. In the seventhembodiment, a near-field exposure mask having an antireflection filmformed on the near-field exposure mask 61 of the fourth embodiment isused.

First, as shown in FIG. 12( a), a resist layer 54 is formed on a Sisubstrate 52 by an application technique such as a spin coatingtechnique, as in the fourth embodiment. As shown in FIG. 12( a), anear-field exposure mask 61B having a near-field light generating filmpattern 66 a and an antireflection film 70 formed on a Si substrate 62is prepared. The antireflection film 70 is formed by a vapor depositiontechnique on the surface of the Si substrate 62 on the opposite sidefrom the side on which the near-field light generating film pattern 66 ais formed. In the seventh embodiment, the antireflection film 70 isformed by a vapor deposition technique, but is not necessarily formed bythat technique. The antireflection film 70 can be a MgF₂ film, a SiO₂film, a TiO₂ film, a ZnO₂ film, a CeF₃ film, or the like. Theantireflection film 70 can be either a single layer structure or amultilayer structure.

As shown in FIG. 12( b), the near-field light generating film pattern 66a is then brought into contact with the resist layer 54. As shown inFIG. 12( c), a LED of 1550 nm in wavelength is used, and the upper face(the back surface) of the near-field exposure mask 61B is exposed forone hour with an incident power of 60 mW. The incident polarized lightis p-polarized light, and the incident angle is 45 degrees. When theincident angle is greater than 74 degrees as in the fourth embodiment,the reflectivity becomes higher. However, the formation of theantireflection film 70 on the near-field exposure mask 61B can lower thereflectivity of the incident light power. As an exposure is performed,near-field light 68 is generated at the edge portions of the near-fieldlight generating film pattern 66 a, as shown in FIG. 12( d). The resistportions 54 a in the vicinities of the portions at which the near-fieldlight 68 is generated become dissociated through a multistep transitionprocess. The exposed sample is developed for 30 seconds with adeveloper. Cleaning is then performed with pure water, and moisture isremoved by an air blow.

As shown in FIG. 12( e), the exposed resist portions 54 a are dissolvedin the developer, to form a pattern 54 b having a width of 50 nm and adepth of 50 nm, which correspond to the edge portions of the near-fieldlight generating film pattern 66 a.

As described above, according to the seventh embodiment, thereflectivity at the interface between the air and Si can be lowered, andthe exposure time can be shortened.

Eighth Embodiment

Referring now to FIGS. 13( a) through 13(e), a near-field exposuremethod according to an eighth embodiment is described. The eighthembodiment is the same as the seventh embodiment illustrated in FIGS.12( a) through 12(e), except that a subwavelength structure is providedas the antireflection film.

First, as shown in FIG. 13( a), a resist layer 54 is formed on a Sisubstrate 52 by an application technique such as a spin coatingtechnique, as in the fourth embodiment. As shown in FIG. 13( a), anear-field exposure mask 61C having a near-field light generating filmpattern 66 a and a subwavelength structure 72 formed on a Si substrate62 is prepared.

The subwavelength structure 72 is manufactured in the following manner.An electron beam resist is applied to the back surface of the Sisubstrate 62, or to the surface of the Si substrate 62 on the oppositeside from the surface on which the near-field light generating filmpattern 66 a is formed. After patterning is performed on the electronbeam resist by an electron beam lithography apparatus, for example,etching is performed on the Si substrate 62 with a SF₆ gas, for example,with the patterned electron beam resist being used as a mask. In thismanner, the subwavelength structure 72 having two-dimensional conicstructures can be obtained. The conic structure intervals are 400 nm,for example, and the heights of the conic structures are 700 nm, forexample. Although an antireflection film having the subwavelengthstructure 72 is formed by electron beam lithography in the eighthembodiment, the antireflection film is not necessarily formed by thistechnique in the present invention.

As shown in FIG. 13( b), the near-field light generating film pattern 66a of the near-field exposure mask 61C is then brought into contact withthe resist layer 54. As shown in FIG. 13( c), a LED of 1550 nm inwavelength is used, and the back surface of the near-field exposure mask61C is exposed for one hour with an incident power of 60 mW. Theincident polarized light is p-polarized light, and the incident angle is45 degrees. When the incident angle is greater than 74 degrees as in thefourth embodiment, the reflectivity becomes higher. However, theformation of the subwavelength structure 72 on the near-field exposuremask 61C can lower the reflectivity of the incident light power. As anexposure is performed, near-field light 68 is generated at the edgeportions of the near-field light generating film pattern 66 a, as shownin FIG. 13( d). The resist portions 54 a in the vicinities of theportions at which the near-field light 68 is generated becomedissociated through a multistep transition process. The Si substrate 52having the exposed resist layer 54 is developed for 30 seconds with adeveloper. Cleaning is then performed with pure water, and moisture isremoved by an air blow. As a result, the exposed resist portions 54 aare the dissolved in the developer, and a pattern 54 b having a width of50 nm and a depth of 50 nm, which correspond to the edge portions of thenear-field light generating film pattern 66 a, can be formed on the Sisubstrate 52, as shown in FIG. 13( e).

As described above, according to the eighth embodiment, the reflectivityat the interface between the air and Si can be lowered, and the exposuretime can be shortened.

Ninth Embodiment

Referring now to FIGS. 14( a) through 14(e), a near-field exposuremethod according to a ninth embodiment is described. The near-fieldexposure method according to the ninth embodiment is the same as theseventh embodiment illustrated in FIGS. 12( a) through 12(e), exceptthat a multilayer antireflection film is formed as the antireflectionfilm on the back surface of a near-field exposure mask.

First, as shown in FIG. 14( a), a resist layer 54 is formed on a Sisubstrate 52 by an application technique such as a spin coatingtechnique, as in the fourth embodiment. As shown in FIG. 14( a), anear-field exposure mask 61D having a near-field light generating filmpattern 66 a and a multilayer antireflection film 74 formed on a Sisubstrate 62 is prepared. The multilayer antireflection film 74 isformed on the surface of the Si substrate 62 on the opposite side fromthe surface on which the near-field light generating film pattern 66 ais formed. The multilayer antireflection film 74 has a structure inwhich layers are arranged so that the refractive index varies from 1 to3.48 toward the Si substrate 62 from the light incident side (the sidefurthest from the Si substrate 62). In this embodiment, the number oflayers in the multilayer antireflection film 74 is 10, and each of thelayers has a film thickness of 50 nm and is formed by a sputteringtechnique. At the time of sputtering, the refractive indexes of therespective layers are varied by adjusting the O₂ gas mixture ratio in aSi target. Although the antireflection film is formed by a sputteringtechnique in the ninth embodiment, the antireflection film is notnecessarily formed by this technique. MgF₂, SiO₂, TiO₂, ZnO₂, CeF₃,As₂S₃, SrTiO₃, AgCl, or the like can be used as the material of theantireflection film. The number of layers in the antireflection film isnot particularly limited.

As shown in FIG. 14( b), the near-field light generating film pattern 66a of the near-field exposure mask 61D is then brought into contact withthe resist layer 54. As shown in FIG. 14( c), a LED of 1550 nm inwavelength is used, and the back surface of the near-field exposure mask61D is exposed for one hour with an incident power of 60 mW. Theincident polarized light is p-polarized light, and the incident angle is45 degrees. When the incident angle is greater than 74 degrees as in thefourth embodiment, the reflectivity becomes higher. However, theformation of the multilayer antireflection film 74 on the near-fieldexposure mask 61D can lower the reflectivity of the incident lightpower. As an exposure is performed, near-field light 68 is generated atthe edge portions of the near-field light generating film pattern 66 a,as shown in FIG. 14( d). The resist portions 54 a in the vicinities ofthe portions at which the near-field light 68 is generated becomedissociated through a multistep transition process. The Si substrate 52having the exposed resist layer 54 is developed for 30 seconds with adeveloper. Cleaning is then performed with pure water, and moisture isremoved by an air blow. As a result, the exposed resist portions 54 aare dissolved in the developer, and a pattern 54 b having a width of 50nm and a depth of 50 nm, which correspond to the edge portions of thenear-field light generating film pattern 66 a, can be formed on the Sisubstrate 52, as shown in FIG. 14( e).

As described above, according to the ninth embodiment, the reflectivityat the interface between the air and Si can be lowered, and the exposuretime can be shortened.

Tenth Embodiment

Referring now to FIGS. 15( a) through 15(e), a near-field exposuremethod according to a tenth embodiment is described. The near-fieldexposure method according to the tenth embodiment is the same as theseventh embodiment illustrated in FIGS. 12( a) through 12(e), exceptthat a multilayer antireflection film 76 is formed as the antireflectionfilm on the back surface of a near-field exposure mask.

First, as shown in FIG. 15( a), a resist layer 54 is formed on a Sisubstrate 52 by an application technique such as a spin coatingtechnique, as in the fourth embodiment. As shown in FIG. 15( a), anear-field exposure mask 61E having a near-field light generating filmpattern 66 a and the antireflection film 76 formed on a Si substrate 62is prepared. The antireflection film 76 has a structure in which thinfilms with a low refractive index and thin films with a high refractiveindex are alternately stacked. In the antireflection film 76 in thisembodiment, SiO₂ layers and TiO₂ layers are alternately stacked by usinga sputtering technique, the number of layers is 4, and each of thelayers has a film thickness of 50 nm. Although the antireflection filmis formed by a sputtering technique in this embodiment, theantireflection film is not necessarily formed by this method. MgF₂,SiO₂, TiO₂, ZnO₂, CeF₃, As₂S₃, SrTiO₃, AgCl, or the like can be used asthe material of the antireflection film. The number of layers in theantireflection film is not particularly limited.

As shown in FIG. 15( b), the near-field light generating film pattern 66a of the near-field exposure mask 61E is then brought into contact withthe resist layer 54. As shown in FIG. 15( c), a LED of 1550 nm inwavelength is used, and the back surface of the near-field exposure mask61E is exposed for one hour with an incident power of 60 mW. Theincident polarized light is p-polarized light, and the incident angle is45 degrees. When the incident angle is greater than 74 degrees as in thefourth embodiment, the reflectivity becomes higher. However, theformation of the multilayer antireflection film 76 on the near-fieldexposure mask 61E can lower the reflectivity of the incident lightpower.

As an exposure is performed in the above manner, near-field light 68 isgenerated at the edge portions of the near-field light generating filmpattern 66 a, as shown in FIG. 15( d). The resist portions 54 a in thevicinities of the portions at which the near-field light 68 is generatedbecome dissociated through a multistep transition process. The exposedsample is developed for 30 seconds with a developer. Cleaning is thenperformed with pure water, and moisture is removed by an air blow. As aresult, the exposed resist portions 54 a are dissolved in the developer,and a pattern 54 b having a width of 50 nm and a depth of 50 nm, whichcorrespond to the edge portions of the near-field light generating filmpattern 66 a, can be formed on the Si substrate 52, as shown in FIG. 15(e).

As described above, according to the tenth embodiment, the reflectivityat the interface between the air and Si can be lowered, and the exposuretime can be shortened.

Eleventh Embodiment

Referring now to FIGS. 16( a) through 18, a pattern forming methodaccording to an eleventh embodiment is described. The pattern formingmethod according to the eleventh embodiment is a method established bycombining a nanoimprint method and a near-field exposure method.

First, as shown in FIGS. 16( a) and 16(b), a Si substrate 80 isprepared, and a light-curable resin film 82 is formed on the Sisubstrate 80. The light-curable resin film 82 may be formed by a spinnertechnique, for example. By the spinner technique, the number ofrotations of the spinner is controlled by taking into account theviscosity and solid content of the light-curable resin film 82, and theevaporation rate of the solvent. In this manner, a desired filmthickness can be obtained. After the formation of the light-curableresin film 82, prebake can be performed to remove the solvent containedin the film.

As shown in FIG. 16( c), a template 90 having a near-field lightgenerating film pattern 94 formed on a Si substrate 92 is prepared. Thistemplate 90 can be a near-field exposure mask according to the firstembodiment or any of the fourth through tenth embodiments. Thelight-curable resin film 82 formed on the Si substrate 80 is thenbrought into contact with the near-field light generating film pattern94 of the template 90 (FIG. 16( d)).

With the light-curable resin film 82 and the near-field light generatingfilm pattern 94 being in contact with each other, light is emitted ontothe back surface side of the silicon substrate 80 or the opposite sidefrom the side on which the light-curable resin film 82 is formed. Thelight irradiation is performed for 0.1 to 20 seconds. As a result,near-field light is generated at the edge portions of the near-fieldlight generating film pattern 94 of the template 90, and the generatednear-field light reaches the light-curable resin film 82. Since thelight emitted in this embodiment is so-called nonresonant light, thelight-curable resin film 82 reacts directly to the emitted light, but isnot chemically changed at all when the irradiation time and intensityare adjusted. In the step illustrated in FIG. 16( d), the distancebetween the Si substrate 80 having the light-curable resin film 82applied thereto and the template 90 can be determined based on thewavelength of the emitted light. In this embodiment, the template 90 isa template having the near-field light generating film pattern 94 formedon the Si substrate 92. However, the template 90 can be a concave-convexmold, and the material of the concave-convex mold can be Si.

FIG. 18 shows a photograph indicating that near-field light is generatedat the concave and convex edge portions that correspond to the pattern94 of the template 90. As can be seen from FIG. 18, the light intensityof the near-field light is higher at the concave and convex edgeportions. The light-curable resin film 82 reacts to the generatednear-field light. As a result, the light-curable resin film 82 is curedat local regions 82 a corresponding to the above-mentioned edgeportions, as shown in FIG. 17( a).

As shown in FIG. 17( b), the template 90 is detached from the Sisubstrate 80. The edge neighborhood portions 82 a formed by curing thelight-curable resin film 82 with the near-field light generated in thestep illustrated in FIG. 16( e) adhere tightly to the template 90.Therefore, the cured light-curable resin film portions 82 a aredetached, together with the template 90, from the Si substrate 80. Onthe other hand, the light-curable resin film portions 82 b that do nothave near-field light generated and are located outside the edgeneighborhood portions 82 a are not cured and are soft in the stepsillustrated in FIG. 16. Therefore, the portions 82 b are not detachedwith the template, but remain on the Si substrate 80 (FIG. 17( b)).

The light-curable resin film portions 82 b remaining on the Si substrate80 is used as a mask, and etching is performed on the Si substrate 80.In this manner, a silicon substrate 80 a having a fine pattern can beobtained.

The near-field light generating film pattern 94 of the template 90 ismade of a metal containing at least one element selected from the groupconsisting of Au, Al, Ag, Cu, and Cr, and the film thickness of thepattern 94 may be greater than 0 nm and not greater than 40 nm. Thelight to be emitted can have a wavelength of 1 μm to 5.0 μm. Further,light can be emitted onto the template 90. The light-curable resin film82 can not be cured by light having a wavelength of 1 μm to 5.0 μm.

As shown in FIG. 18, the concave edge portions of the concave-convexmold serve as an even finer pattern. That is, by the nanoimprint methodto which this embodiment is applied, the light-curable resin film can belocally cured by near-field light rapidly enhanced at the concave andconvex edge portions, to form a sharp detachment face at the time ofdetachment. In this manner, a much finer pattern than a pattern formedwith concavities and convexities can be formed. At the concave andconvex edge portions, sharper electrical field gradients exist,depending on emitted light. However, a diabatic process that reacts onlyin those regions can be used. Accordingly, fine patterning of 10 nm orsmaller can be performed with high precision.

FIG. 19 shows template materials, substrate materials, the wavelengthsof injection light sources, and the wavelengths of light-curable resinsthat are used in Examples 1 through 8 according to this embodiment. FIG.20 shows template materials, substrate materials, the wavelengths ofinjection light sources, and the wavelengths of light-curable resinsthat are used in Comparative Examples 1 through 4 of this embodiment. InFIGS. 19 and 20, the template materials are the materials for thesubstrate 92 of the template 90, and the substrate materials are thematerials for the substrate 80 on the side to be exposed. The templatematerials and the substrate materials are Si or glass. In FIGS. 19 and20, double circles indicate “very good”, single circles indicate “good”,and triangles indicate “not very good.”

As described above, according to the eleventh embodiment, a pattern istransferred by combining a nanoimprint method and a near-field exposuremethod. Accordingly, a fine pattern can be formed.

Twelfth Embodiment

Referring now to FIG. 21, a near-field optical lithography methodaccording to a twelfth embodiment is described.

A near-field exposure method and a near-field optical nanoimprint methodare lithography techniques involving near-field light generating membersas masks or templates, and are designed for generating near-field lightfrom light having a longer wavelength than the wavelength of propagatinglight that is normally emitted. It is known that, with the use ofnear-field light, a photochemical reaction occurs in the resist at ashorter wavelength at which a reaction does not normally occurs.Accordingly, no reactions occur at portions irradiated only withpropagating light from which near-field light is not generated, but aphotochemical reaction occurs only at the portions where near-fieldlight exists, to enable patterning. This is a phenomenon that occursboth in the case of a near-field exposure method and in the case of anear-field optical nanoimprint method.

Near-field light with high intensity is focused locally onto portionswith small radii of curvature in the surface. That is, the electricalfield intensity of near-field light tends to become higher at portionsnear the corners. Therefore, in a light exposure using nanoimprint or amask, patterning is performed depending on the line shapes of the maskor a template. However, if an exposure or imprint curing occurs only atboth sides of the mask in the mask width direction, the patternedlinewidth becomes smaller by half or more, and the number of lines isdoubled. That is, with the use of near-field light, finer patterning canbe performed.

By the near-field optical lithography method according to the twelfthembodiment, the near-field light generating member 100 illustrated inFIG. 21 is used as a near-field exposure mask or a template. In thenear-field light generating member 100, at least one convex portion 104is formed on one of the facing surfaces of a transparent substrate 102.The substrate 102 and the convex portion 104 can be made of differentmaterials from each other, or may be made of the same material. Examplesof materials of the respective substrates include Si, SiO₂, sapphire,magnesium fluoride, zinc sulfide, zinc selenide, and calcium fluoride.The convex portion 104 includes a top end 104 a and sides 104 b. Thesides 104 b are side faces that connect the top end 104 a and thesubstrate 102. The top end 104 a and the sides 104 b are covered with anear-field light generating layer 106 that is made of metal, CNT (carbonnanotube), or graphene. Specifically, the near-field light generatinglayer 106 includes a first layer 106 a covering the top end 104 a of theconvex portion 104, and a second layer 106 b covering the sides 104 b ofthe convex portion 104. Further, a third layer 106 c made of metal, CNT(carbon nanotube), or graphene can be or may not be formed in the regionother than the convex portion 104 on the surface of the substrate 102 onwhich the convex portion 104 is formed.

The near-field light generating member 100 is positioned so that asubstrate 120 on which a photosensitive resin layer (a resist layer) 122is formed, and the photosensitive resin layer 122 face the convexportion 104. In this situation, light is emitted onto the back surfaceof the near-field light generating member 100, or onto the surface onthe opposite side from the surface on which the convex portion 104 isformed. In this manner, near-field light is generated from thenear-field light generating layer 106, and the photosensitive resinlayer 122 is exposed by the near-field light. If the substrate 120 is atransparent substrate, light can be emitted onto the substrate 120.

Metal, CNT (carbon nanotube), and graphene has the function to generateand guide near-field light. Near-field light generated by any of thosematerials has excellent polarization components in the travelingdirection (the direction from the substrate toward the top end of theconvex portion in the side faces of the convex portion) or has excellentso-called z-polarized light (light polarized in the travelingdirection), compared with the polarization components of general planewave propagation light that are perpendicular to the travelingdirection. Therefore, the near-field light is suitable for the use inthe lithography technology, and has double patterning properties.Accordingly, stronger double patterning can be performed, if a resistformed by the lithography technology or the polymerization initiator ofa curable resin in a nanoimprint method strongly reacts to z-polarizedlight.

Further, by reducing the width of the convex portion, fine patterning,if not double patterning, can be performed.

Example 1

Examples 1 through 4 in which the film thicknesses of the respectivecomponents in the near-field light generating layers 106 were variedwere prepared as near-field light generating members 100. Cr was used asthe material of the near-field light generating layers 106. Light of 532nm in wavelength was emitted onto each substrate 102, and the lightintensity distributions in the convex portions 104 of the near-fieldlight generating members 100 were examined with a near-field opticalmicroscope. Each convex portion 104 was a line-and-space structure of100 nm/100 nm, and the height of each convex portion 104 was 450 nm. Thelight intensity distributions do not depend on the sizes ofline-and-space structures and the heights of convex portions.

The results of the examination are shown in Table 1 (shown below) andFIGS. 22A through 22D. In Table 1, “a,” “b,” and “c” represent the filmthicknesses of the first layer 106 a, the second layer 106 b, and thethird layer 106 c of each near-field light generating layer 106. FIGS.22A through 22D are graphs showing the light intensity distributions inthe samples 1 through 4.

To have almost equal intervals between the lines formed by doublepatterning, the width of the convex portion 104 of each near-field lightgenerating member 100 should be almost a half a space interval.

TABLE 1 a b c EVALUATION SAMPLE 1 50 nm 10 nm 50 nm  good SAMPLE 2 50 nm10 nm 0 nm excellent SAMPLE 3 20 nm  5 nm 0 nm very good SAMPLE 4 100nm  20 nm 0 nm not good

Double patterning was not properly performed in the sample 4, but wasperformed in the samples 1 through 3. The peak intensity ratios amongthe respective double-patterned structures were 8:27:22:2 (sample 1:sample 2: sample 3: sample 4). Therefore, the samples 2 and 3 werepreferable, and the sample 2 was particularly preferable. This isbecause the near-field light generated at the sides 104 b was guidedtoward the top end 104 a, and reached the corners of the top end 104 a,to enhance the optical electric-field at the corners. A simulation wasperformed on the same structures as above by the FDTD (Finite-DifferenceTime-Domain) method. As a result, z-polarization components, orparticularly the electric fields at the corner portions, were enhanced.Therefore, if the resist in lithography or the polymerization initiatorof the curable resin in nanoimprint strongly reacts to z-polarizedlight, stronger double patterning can be performed. By spin coating, theresin main chain is readily oriented in the in-plane direction orparticularly in the radial direction of motion (the direction from thecenter to the outside). Accordingly, the above characteristics can beachieved by appropriately modifying the resist resin structure.

With the samples 1 through 4 being used as masks, the to-be-exposedsubstrate 120 having the resist 122 applied thereonto was placed on thelight shielding side of the near-field exposure mask 100, as shown inFIG. 21. Exposures were then performed. Examples of positive resiststhat can be used here include a diazonaphthoquinone-novolac resist and achemically-amplified positive resist. Examples of negative resists thatcan be used include a chemically-amplified negative resist, a photocation polymerizable resist, a photo radical polymerizable resist, apolyhydroxystyrene-bisazide resist, a cyclized rubber-bisazide resist,and a polyvinyl cinnamate resist. Exposures were performed on thoseresists, and the obtained clear double-patterned shapes were evaluatedas shown in Table 1.

In the case of line patterning, the polarized light to be emitted ispreferably p-polarized light. In this case, p-polarized light ispolarized light having the electrical field of the light irradiation ina direction perpendicular to the pattern length direction.

Other than Cr, the following metals can be used: Au, Al, Ag, Cu, Cr, Sb,W, Ni, In, Ge, Sn, Pb, Zn, and Pd. Where a graphene film, instead of ametal film, was formed, double patterning was also performed. Where acarbon nanotube film was formed, the effects of double patterning werealso confirmed.

Example 2

The parameter ranges in which double patterning was possible in Example1 were examined. The results showed that “a” was 15 to 80 nm, “b” was 2nm to 20 nm, and “c” was 0 nm to 80 nm. Where “a” was greater than “c,”and “b” was greater than “c,” clearer double-patterned structures wereobserved. If the third layer 106 c exists or is thick, the intensity ofthe near-field light generated in the side faces becomes lower. This isbecause light is absorbed in the third layer 106 c prior to generationof near-field light, and becomes weaker. Further, a better result wasachieved where “a” was greater than “b.” This is because the near-fieldlight inside the convex portion 104 and the near field light outside theconvex portion 104 can be both used, if the film thickness of each sideface is smaller than the film thickness of the top end.

To perform film formation under the above described conditions, thesource direction is set in diagonal directions, and film formation isperformed from the two directions, as shown in FIGS. 23( a) and 23(b).The film forming method is normally a vapor deposition method, asputtering method, or MBE, but is not limited to those methods. Byadjusting the angle of irradiation from the irradiation source, the filmthicknesses and film thickness ratios of the first layer 106 a, thesecond layer 106 b, and the third layer 106 c can be adjusted.

Example 3

The near-field light generating members 100 of the samples 1 through 4used in Example 1 were used as nanoimprint templates, and imprintlithography was performed. In the UV-curable resin, acrylic ester wasused as the matrix, and benzophenone, thioxanthone, or 2,4diethylthioxanthone was used as the polymerization initiator. However,the matrix and the polymerization initiator are not limited to thosematerials. The precursor solution for the UV-curable resin was appliedto the substrate, and a glass plate of 5 cm in thickness was placed as aweight on the template, to press the template against the substrate. Theirradiation light was light of 488 nm, instead of a ultraviolet ray.After the irradiation, the template was detached from the substrate, andthe unsolidified precursor solution was removed. As a result, adouble-patterned shape was confirmed.

Example 4

The parameter ranges in which double patterning was possible in Example3 were examined. The results showed that “a” was 15 nm to 80 nm, “b” was2 nm to 20 nm, and “c” was 0 nm to 80 nm. Where “a” was greater than“c,” and “b” was greater than “c,” clearer double-patterned structureswere observed. Even clearer double-patterned structures were achievedwhere “a” was greater than “b.”

As described above, according to the twelfth embodiment, doublepatterning can be efficiently performed by a near-field exposure methodusing a resist or a nanoimprint method, and the processing accuracy formasks and templates can be increased.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel methods and systems describedherein can be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein can be made without departing from the spiritof the inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the inventions.

1. A near-field exposure mask comprising: a silicon substrate; and anear-field light generating unit formed on the silicon substrate, thenear-field light generating unit being a layer containing at least oneelement selected from the group consisting of Au, Al, Ag, Cu, Cr, Sb, W,Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formed with layersmade of some of those materials.
 2. The mask according to claim 1,wherein a height of at least part of the near-field light generatingunit is 50 nm or less.
 3. A resist pattern forming method, comprising:bringing a resist layer into contact with the near-field exposure maskof claim 1, the resist layer being formed on a substrate to beprocessed; and patterning the resist layer to form a resist pattern byinjecting light from a light source onto the resist layer via thenear-field exposure mask, the light having a wavelength of 1 μm to 20μm.
 4. The method according to claim 3, wherein the resist layer has amultilayer stack structure, and the patterning of the resist layerincludes: patterning an uppermost layer of the multilayer stackstructure by injecting the light from the light source onto theuppermost layer via the near-field exposure mask, the light having thewavelength of 1 μm to 20 μm; and patterning on the resist layer as alower layer, with the patterned uppermost layer being used as a mask. 5.A device manufacturing method, comprising performing etching on thesubstrate to be processed, using a resist pattern formed by the resistpattern forming method of claim
 4. 6. A near-field exposure method,comprising injecting light onto a resist layer formed on a secondsubstrate, using a near-field exposure mask formed on one of surfaces ofa transparent first substrate, the near-field exposure mask including anear-field light generating unit containing at least one elementselected from the group consisting of Au, Al, Ag, Cu, Cr, Sb, W, Ni, In,Ge, Sn, Pb, Zn, Pd, and C, the injecting of light including arrangingthe near-field light generating unit in contact with the resist layer,the light entering from a direction inclined with respect to aperpendicular of a surface of the first substrate on the opposite sidefrom the surface on which the near-field light generating unit isformed, or a perpendicular of a surface of the second substrate on theopposite side from a surface on which the resist layer is formed, thelight being p-polarized light.
 7. The method according to claim 6,wherein the first and second substrates are made of Si.
 8. The methodaccording to claim 6, wherein the light enters through the surface ofthe first substrate on the opposite side from the surface on which thenear-field light generating unit is formed, an incident angle of thelight being 57 degree to 82 degree.
 9. The method according to claim 6,wherein the light enters through the surface of the second substrate onthe opposite side from the surface on which the resist layer is formed,an incident angle of the light being 26 degree to 47 degree.
 10. Themethod according to claim 6, wherein the light enters through thesurface of the first substrate on the opposite side from the surface onwhich the near-field light generating unit is formed, and the near-fieldexposure mask includes an antireflection film on the surface of thefirst substrate on the opposite side from the surface on which thenear-field light generating unit is formed.
 11. The method according toclaim 6, wherein a height of at least part of the near-field lightgenerating unit is 50 nm or less.
 12. A pattern forming method,comprising: pressing a template against a second substrate having alight-curable resin applied to a surface thereof, the template includinga transparent first substrate and a near-field light generating unitthat is formed on the first substrate, the near-field light generatingunit being a layer containing at least one element selected from thegroup consisting of Au, Al, Ag, Cu, Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn,Pd, and C, or a film stack formed with layers made of some of thosematerials; injecting light to a side of the first substrate, the lighthaving a wavelength of 1 μm to 5 μm; and causing the light-curable resinto react to near-field light generated from the near-field lightgenerating unit, the near-field light being generated by the injectedlight.
 13. The method according to claim 12, wherein the near-fieldlight generating unit includes a concave-convex pattern.
 14. The methodaccording to claim 12, wherein the light-curable resin does not react tothe light having the wavelength of 1 μm to 5 μm.
 15. A near-fieldoptical lithography member comprising: a transparent substrate; a convexportion formed on one of surfaces of the substrate; and a near-fieldlight generating layer that covers a top end of the convex portion andsides of the convex portion, the sides connecting the top end and thesubstrate, the near-field light generating layer being made of Au, Al,Ag, Cu, Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, or C.
 16. The memberaccording to claim 15, wherein a film thickness of a portion of thenear-field light generating layer covering the top end of the convexportion is greater than a film thickness of each portion of thenear-field light generating layer covering the sides of the convexportion.
 17. The member according to claim 15, wherein the near-fieldlight generating layer is also formed on a region of the one of thesurfaces of the substrate other than the convex portion, and a filmthickness of each portion of the near-field light generating layercovering the top end and the sides of the convex portion is greater thana film thickness of a portion of the near-field light generating layerformed on a region of the one of the surface of the substrate other thanthe convex portion.
 18. The member according to claim 15, wherein thesubstrate is made of a material different from a material of the convexportion.
 19. The member according to claim 15, wherein a thickness of aportion of the near-field light generating layer covering the top end ofthe convex portion is 15 nm to 80 nm, and a thickness of each portion ofthe near-field light generating layer covering the sides is 2 nm to 20nm.
 20. A near-field exposure method, comprising performing a near-fieldexposure, using the near-field optical lithography member of claim 15 asa near-field exposure mask.
 21. A near-field nanoimprint method,comprising performing near-field nanoimprint, using the near-fieldoptical lithography member of claim 15 as a near-field nanoimprinttemplate.